A document scanner ordinarily employs a traveling scanner carriage in which a scanner lamp is mounted for illuminating a document to be scanned. As is well known, reflectors are also typically mounted on the carriage adjacent to the lamp for helping to increase the amount of light projected by the scanner lamp onto the area of the document being scanned.
One of the problems associated with scanning such a document is the non-uniformity of the illumination levels across the document being scanned. In this regard, the amount of light at the marginal edges of the document is always less that the illumination levels at about the center of the document. As a result of this non-uniformity, the excessive illumination levels at the center of the document may cause undesired and unwanted saturation of the translational devices utilized to convert detected light into an associated electrical signal. Alternatively the irregular illumination pattern may cause such a translation device to have such a low signal to noise ratio that a significant loss of resolution results in the less illuminated areas of the document.
Therefore it would be highly desirable to have a new and improved method and light reflection device that enables the light distribution pattern across a document being scanned to be uniformly illuminated substantially from edge to edge.
One attempt at seeking to provide a uniform document illumination area has been to utilize a separate light dispersion device with a preformed aperture that is oriented above the scanner lamp. In order to control the light reflected onto the document, the aperture is configured to be wider at its end portions and narrower at its center to provide what is commonly called a "dog bone" illumination profile.
While the use of such a separate light dispersion device has been found to be satisfactory for some applications, such a device utilizes unnecessary space and substantially increases manufacturing costs and assembly time.
Therefore it would be highly desirable to have such a new and improved method and light reflection device that does not increase manufacturing costs and assembly time unnecessarily nor require the utilization of additional space.
Another attempt at seeking to provide a uniform document illumination area has been to employ the use of additional reflectors at about the end portions of the scanner lamp in a stop field opposite from the scanner lamp. Again, while the use of such additional reflector may help to uniformly disperse the illumination from the scanner lamp, the increased costs and space requirements associated with such additional reflectors has not been entirely satisfactory.
Therefore it would be highly desireable to have such a new and improved apparatus and method of light dispersion that provides a uniform document illumination area without the need of additional reflectors.